The present invention relates to a semiconductor integrated circuit device, and more particularly to a semiconductor integrated circuit device (which will be referred to hereinafter as "MISIC") which is constructed of insulated gate type field effect transistors (which will be referred to hereinafter as "MISFETs").
An abnormally high voltage due to frictional static electricity is frequently applied to the external terminals of an MISIC during transportation or handling.
The gate insulating film of a MESFET usually has such a relatively low breakdown voltage that it is broken down when the abnormally high voltage is applied to the gate electrode thereof.
In order to prevent the breakdown, therefore, a gate protecting element or circuit is usually provided in the MISIC in a manner to correspond to its MISFET for receiving an external signal.
However, the investigations of the Inventors have revealed that the abnormally high voltage will break down the gate insulating film of not only the signal receiving MISFET but also a signal output MISFET of the MISIC. As a result, the MISIC is rendered substantially inoperative when its signal output MISFET is broken down, although the signal receiving MISFET is protected against the abnormal voltage by providing the gate protecting means at the signal receiving external terminal thereof.